U.S. Pat. No. 5,202,680 (Savage; published 13 Apr. 1993) discloses a system for automatic tallying of drill string components. In the Savage patent, an identification (ID) tag reader antenna, connected to a reader by means of wiring or cable, is placed between a rotary table and a bell nipple. Uniquely-coded electronic ID tags are embedded in recesses in pin ends of components of a drill string. As the drill string moves through the rotary table and bell nipple and past the reader antenna, each ID tag receives an electromagnetic (EM) signal from the reader antenna via its own internal antenna. The Savage patent discloses that the energy received from the reader transmission by the ID tag is sufficient to enable the ID tag to retransmit a uniquely-coded binary signal back to the reader. The Savage patent discloses that the tallies collected could be used to compute and record various service factors that serve as a measure of wear and useful service life of drill string components.
U.S. Patent Application Publication No. 2002/0158120 (Zierolf; published 31 Oct. 2002) discloses a process and assembly for identifying and tracking assets such as tubulars. In the Zierolf publication, tubulars in a tubing string are tagged with radio frequency identification (RFID) devices. An external antenna is electrically connected to each RFID device to extend the read range of the RFID device. The Zierolf publication reports a read range of up to 15 inches or more with the external antenna. A handheld transceiver connected to a handheld wand is used to read the RFID devices. The handheld wand is held manually adjacent to the tubulars or can be secured in a stationary position adjacent to the tubulars. The transceiver transmits a radio frequency (RF) in the direction of the tubing string through the wand. As the antenna on a given tubular passes the wand, the signal coming out of the wand is received by the antenna and transmitted to the corresponding RFID device. The RFID device detects the signal and sends a RF response through the antenna and wand to the transceiver.
There are various challenges in designing a system that automatically tracks pipe activity on a rig. For example, there is a limited vertical free air space between the rotary table and the bell nipple due to horizontal steel surfaces that clip the magnetic fields in this space. The vertical free air space dictates the time available for communication between the reader antenna and an ID tag. The challenge then becomes whether the reader antenna placed underneath the rotary table will have sufficient time to power up and read the ID tag while the pipe carrying the ID tag is moving vertically through the rotary table and bell nipple. There are also electrical and EM noises on the rig that could interfere with the readings made via the reader antenna. In many cases, rigs do not follow standard electromagnetic compatibility guidelines. This means that some machinery and wiring on rigs will have electromagnetic field leakage from wiring that may interfere with the operation of other machinery or instrumentation on the rig.